/** * 
 * * Base64 encode / decode * 
 * * @author haitao.tu 
 * * @date 2010-04-26 
 * * @email tuhaitao@foxmail.com * */
function Base64() {
	// private property  
	_keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
	// public method for encoding  
	this.encode = function(input) {
			var output = "";
			var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
			var i = 0;
			input = _utf8_encode(input);
			while(i < input.length) {
				chr1 = input.charCodeAt(i++);
				chr2 = input.charCodeAt(i++);
				chr3 = input.charCodeAt(i++);
				enc1 = chr1 >> 2;
				enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
				enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
				enc4 = chr3 & 63;
				if(isNaN(chr2)) {
					enc3 = enc4 = 64;
				} else if(isNaN(chr3)) {
					enc4 = 64;
				}
				output = output + _keyStr.charAt(enc1) + _keyStr.charAt(enc2) + _keyStr.charAt(enc3) + _keyStr.charAt(enc4);
			}
			return output;
		}
		// public method for decoding  
	this.decode = function(input) {
			var output = "";
			var chr1, chr2, chr3;
			var enc1, enc2, enc3, enc4;
			var i = 0;
			input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
			while(i < input.length) {
				enc1 = _keyStr.indexOf(input.charAt(i++));
				enc2 = _keyStr.indexOf(input.charAt(i++));
				enc3 = _keyStr.indexOf(input.charAt(i++));
				enc4 = _keyStr.indexOf(input.charAt(i++));
				chr1 = (enc1 << 2) | (enc2 >> 4);
				chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
				chr3 = ((enc3 & 3) << 6) | enc4;
				output = output + String.fromCharCode(chr1);
				if(enc3 != 64) {
					output = output + String.fromCharCode(chr2);
				}
				if(enc4 != 64) {
					output = output + String.fromCharCode(chr3);
				}
			}
			output = _utf8_decode(output);
			return output;
		}
		// private method for UTF-8 encoding  
	_utf8_encode = function(string) {
			string = string.replace(/\r\n/g, "\n");
			var utftext = "";
			for(var n = 0; n < string.length; n++) {
				var c = string.charCodeAt(n);
				if(c < 128) {
					utftext += String.fromCharCode(c);
				} else if((c > 127) && (c < 2048)) {
					utftext += String.fromCharCode((c >> 6) | 192);
					utftext += String.fromCharCode((c & 63) | 128);
				} else {
					utftext += String.fromCharCode((c >> 12) | 224);
					utftext += String.fromCharCode(((c >> 6) & 63) | 128);
					utftext += String.fromCharCode((c & 63) | 128);
				}
			}
			return utftext;
		} // private method for UTF-8 decoding  
	_utf8_decode = function(utftext) {
		var string = "";
		var i = 0;
		var c = c1 = c2 = 0;
		while(i < utftext.length) {
			c = utftext.charCodeAt(i);
			if(c < 128) {
				string += String.fromCharCode(c);
				i++;
			} else if((c > 191) && (c < 224)) {
				c2 = utftext.charCodeAt(i + 1);
				string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
				i += 2;
			} else {
				c2 = utftext.charCodeAt(i + 1);
				c3 = utftext.charCodeAt(i + 2);
				string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
				i += 3;
			}
		}
		return string;
	}
}